1. Field of the Invention
The present invention relates to a transmission equipped with a planetary gear mechanism which has an element to be fixed to a transmission casing, and also relates to a planetary gear mechanism.
2. Description of Related Art
In case an element such as a ring gear, a carrier, or the like of a planetary gear mechanism is fixed to a transmission casing in the above-described kind of conventional transmission, the above-described element is engaged with the transmission casing by means of a spline so as not to be rotatable relative to the transmission casing, and is fixedly engaged by a snap ring so as to be relatively immovable in an axial direction (see Japanese Published Unexamined Patent Application No. 203740/1989). In order to facilitate the assembling work of the transmission, it is desirable to take the following steps. Namely, in an open space outside the transmission casing, transmission constituting elements including a planetary gear mechanism assembled around shaft members of the transmission in sequence in an axial direction. Thereafter, these transmission constituting elements are contained or put inside the transmission casing.
However, in the above-described conventional transmission in which that element of the planetary gear mechanism which is to be fixed is fixedly engaged by a snap ring in a manner not to be movable in the axial direction, there is the following disadvantage. Namely, if another transmission constituting element is present on this side of the planetary gear as seen from an open end of the transmission casing, this transmission constituting element in question will be an obstacle to the mounting of the snap ring. It follows that the planetary gear mechanism cannot be sub-assembled together with this transmission constituting element around a shaft member. As a consequence, the assembly work of the transmission constituting elements into the transmission casing must be made from the innermost element in sequence toward the outermost element, resulting in a troublesome assembly work of the transmission.
In view of the above points, the present invention has an object of providing a transmission in which that element of the planetary gear which is to be fixed can be fixed to the transmission casing from an outside of the peripheral wall portion of the transmission casing so that the workability in the assembly work can be improved.
Further, among the planetary gear mechanisms to be built into the transmission, there is one in which a sun gear is coupled to a power transmission member which is disposed on one axial side of the planetary gear mechanism. One of a ring gear and a carrier, e.g., the carrier is coupled to a transmission member which is disposed on the axially opposite side of the planetary gear mechanism. In this kind of planetary gear mechanism, the following arrangement was employed in the conventional art. Namely, the sun gear and the carrier are fixed by welding or the like to the corresponding power transmission member. In the steps of assembling the transmission, the sun gear and the carrier are assembled in sequence around the shaft of the transmission together with the corresponding power transmission member, thereby assembling the planetary gear mechanism.
However, in the above-described conventional art, if the power transmission member on one axial side and the power transmission member on the axially opposite side deviate in the axial position, the axial position of the sun gear and the carrier to be fixed to these power transmission members also axially deviate. In order to prevent the sun gear and the carrier from giving rise to the mutual interference, there is secured a larger axial clearance than an amount of deviation anticipated between the sun gear and the carrier. As a result, there is a disadvantage in that the planetary gear mechanism occupies a larger axial space. In addition, when the carrier is assembled, a plurality of planetary pinions to be carried on the carrier must be brought into gearing mesh with the sun gear. Therefore, it takes time to assemble the carrier. If the sun gear and the carrier are assembled in the steps of assembling the transmission as in the conventional way, the assembling work of the transmission becomes troublesome.
In view of the above points, the present invention has another object of providing a planetary gear mechanism which has a smaller space in the axial direction and which has an improved workability in assembling.
In planetary gear mechanisms to be built into the transmission, there is one having the following construction. Namely, that carrier of a planetary gear mechanism which rotatably supports a planetary pinion through a pinion shaft has coupled thereto a cylindrical power transmission member, e.g., a clutch inner member of a hydraulic clutch, which is disposed on one axial side of the planetary gear mechanism. Conventionally, in this kind of planetary gear mechanism, the clutch inner member is fixed to a side plate portion on one axial side of the carrier by means of welding or riveting (see Japanese Published Unexamined Patent Application No. 126136/1984). Further, the following arrangement is conventionally employed. Namely, a shaft hole is respectively formed through the side plate portions on both axial sides of the carrier. A pinion shaft is inserted through the shaft holes and both ends thereof are caulked to thereby prevent the pinion shaft from rotating and from dropping out of position relative to the carrier. The objects of preventing the pinion shaft from rotating are as follows. Namely, in order to supply lubricating oil to bearings on the outer circumference of the pinion shaft, the pinion shaft is fixed such that a radial oil hole formed in the pinion shaft comes into a phase which faces a radial direction of the carrier. In this manner, the lubricating oil is efficiently supplied to the bearings by a centrifugal force due to the rotation of the carrier.
However, as in the above-described conventional example, if the clutch inner member is welded to the carrier, the carrier and the clutch sometimes give rise to thermal strains. Also in case the clutch inner member is riveted to the carrier, it is necessary to mount the clutch inner member on the carrier in a step which is other than the step of mounting the pinion shaft to the carrier by caulking. As a result, it takes much time in assembling the carrier, resulting in a high cost.
In view of the above points, the present invention has still another object of providing a low-cost planetary gear mechanism in which the power transmission member and the pinion shaft can be fixed while preventing them from rotating relative to the carrier only by preventing, from being axially pulled out of position, a cylindrical power transmission member to be disposed in one axial side of the planetary gear mechanism and the pinion shaft.
In order to attain the above and other objects, according to a first feature of the present invention, there is provided a transmission equipped with a planetary gear mechanism which has an element to be fixed to a transmission casing, wherein a cylinder portion of a hydraulic brake to be built in the transmission is disposed around the planetary gear mechanism and the element is fixed to the cylinder portion, and wherein the cylinder portion is fixed to the transmission casing by a fixing member which is insertable into the transmission casing from an outside of a peripheral wall portion of the transmission casing.
According to the above-described first feature of the present invention, when the transmission constituting members including the planetary gear mechanism and the hydraulic brake are sub-assembled in an open space outside the transmission casing to thereby assemble the inner elements of the transmission, the following steps may be taken. Namely, that element of the planetary gear mechanism which is to be fixed is fixed to the cylinder portion of the hydraulic brake. After the sub-assembled inner elements are contained inside the transmission casing, the fixing member is inserted into the transmission casing from the outside of the peripheral wall portion, and then the cylinder portion of the hydraulic brake is fixed to the transmission casing. That element of the planetary gear mechanism which is to be fixed is thus fixed to the transmission casing through the cylinder portion of the hydraulic brake. Therefore, even if the transmission constituting members are sub-assembled, the assembling of the transmission can be performed without any problem, resulting in an improved workability in the assembling of the transmission.
Further, if that element of the planetary gear mechanism which is to be fixed is directly fixed to the transmission casing, noises are likely to occur due to the conveyance of the vibrations from this element to the transmission casing. According to the above-described first feature, however, the cylinder portion of the hydraulic brake is interposed between the above-described element and the transmission casing. Therefore, the conveyance of the noises to the transmission casing is restricted, with the result that the noises are reduced.
In order to attain another object as described above, according to another feature of the present invention, there is provided a planetary gear mechanism to be built into a transmission, comprising: that first element of a planetary gear mechanism which is made up of a sun gear; that second element of the planetary gear mechanism which is made up of one of a ring gear and a carrier, the first element and the second element being coupled respectively to a first power transmission member which is disposed on one axial side of the planetary gear mechanism, and to a second power transmission member which is disposed on an axially opposite side of the planetary gear mechanism, wherein the second element has formed therein a cylindrical portion which is inserted into an inner circumference of the first element with a diametrical clearance therebetween; wherein the first element is axially positioned relative to the cylindrical portion through an annular projection which is formed on an inner circumference of the first member, and wherein the first element is coupled to the first power transmission member with an axial play.
According to another feature of the present invention as described above, it is possible to sub-assemble the first element and the second element in advance to thereby couple them together in a manner axially inseparable from each other. Therefore, in the step of assembling the transmission, it is possible to assemble the first element and the second element around the shaft of the transmission in a sub-assembled state. As a result, the assembling work of the transmission becomes easy.
Further, since the first element is axially fixed in position relative to the second element, there is no need of securing an axial clearance in order to prevent the interference between the two elements. The axial space of the planetary gear mechanism can thus be reduced. Even if the first power transmission member for coupling thereto the first element axially deviates relative to the second element, this deviation is absorbed by the play of the first element relative to the first power transmission member. Therefore, there is no disadvantage in axially positioning the first element relative to the second element.
In order to attain still another object as described above, according to still another feature of the present invention, there is provided a planetary gear mechanism to be built into a transmission in which a cylindrical power transmission member which is disposed on one axial side of the planetary gear mechanism is coupled to that carrier of the planetary gear mechanism which rotatably supports a planetary pinion through a pinion shaft. The planetary gear mechanism comprises: a supporting portion which is formed in a side plate portion on one axial side of the carrier, the supporting portion being fitted into the power transmission member; a first engaging portion which is made up of one of a non-circular projection and recess formed in an end surface of the pinion shaft which protrudes through a shaft hole formed in the side plate; and a second engaging portion which is made up of one of a non-circular recess and projection formed in that end surface of the power transmission member which is on a side of the side plate portion, the second engaging portion being engaged with the first engaging portion when the pinion shaft is in a predetermined phase.
When the first and second engaging portions are engaged together, the power transmission member is prevented by the pinion shaft from rotating relative to the carrier. In addition, the pinion shaft is prevented by the power transmission member from rotating relative to the carrier in a predetermined phase. In this manner, simply by preventing, with a suitable means, the power transmission member and the pinion shaft from being axially pulled out of position relative to the carrier, the power transmission member and the pinion shaft can be fixed by preventing them from rotating relative to the carrier. Therefore, a troublesome work of fixing the power transmission member and the pinion shaft to the carrier such as welding or riveting is no longer required, with the result that the assembly work of the carrier becomes easy. In particular, if a first snap ring is mounted on the supporting portion so as to prevent the power transmission member from being pulled out of position relative to the supporting portion, and if a second snap ring is mounted on the pinion shaft so as to prevent the pinion shaft from being axially pulled out of position to thereby prevent the power transmission member and the pinion shaft from being axially pulled out of position, the assembly work of the carrier is further improved.